1. Field of the Invention
The present invention relates to apparatus and method for ultrasonically and electromagnetically stimulating treating tissue, for example, traumatized tissue or a bone injury. More particularly, the present invention relates to apparatus and methods which utilize an ultrasonic transducer assembly in combination with an electromagnetic coil assembly to treat tissue.
2. Description of the Related Art
The use of ultrasound to therapeutically treat and evaluate tissue and bone injuries is known. Impinging ultrasonic pulses having appropriate parameters, e.g., frequency, pulse-repetition, and amplitude, for suitable periods of time and at a proper external location adjacent to a tissue or bone injury has been determined to accelerate the natural healing of, for example, tissue tears, bone breaks and fractures.
U.S. Pat. No. 4,530,360 to Duarte describes a basic non-invasive therapeutic technique and apparatus for applying ultrasonic pulses from an operative surface placed on the skin at a location adjacent a bone injury. To apply the ultrasound pulses during treatment an operator must manually hold the applicator in place until the treatment is complete.
The Duarte patent as well as U.S. Pat. No. 5,520,612 to Winder et al. describe ranges of RF signal for creating the ultrasound, ultrasound power density levels, ranges of duration for each ultrasonic pulse, and ranges of ultrasonic pulse frequencies.
U.S. Pat. No. 5,003,965 to Talish et al. relates to an ultrasonic body treatment system having a body-applicator unit connected to a remote control unit by sheathed fiber optic lines. The signal controlling the duration of ultrasonic pulses and the pulse repetition frequency are generated apart from the body-applicator unit. Talish et al. also describes a mounting fixture for attaching the body-applicator unit to a patient so that the operative surface is adjacent the skin location.
While the systems described in these patents relate to methods and apparatus for ultrasonic diagnosis and/or treatment of hard and soft tissue injuries and defects by applying ultrasound to traumatized tissue, it has been demonstrated that the traumatized tissue heals at a faster rate if the acoustic signal envelope of the applied ultrasonic waves is slowly modulated or perturbed. Modulating the signal envelope of the applied ultrasonic waves can be accomplished by either modulating the envelope of the electrical signal to the ultrasound transducer or by modulating the ultrasonic waves in the body by utilizing-controlled electromagnetic induced forces.
It has also been demonstrated that in the case of a non-union injury, i.e., where a bone fracture fails to heal, that electromagnetic-stimulation (E-stim) treatment of the non-union injury produces a therapeutic response in bone tissue. E-stim generally uses at least an external coil to produce a therapeutic pulsed uniform, electromagnetic field at the fracture site. For example, a pair of Helmholtz coils can produce a constant uniform field at the fracture or wound sites, above the local magnetic field in tissue.
It is generally believed that E-stim promotes and accelerates the healing of non-union injuries due to the creation of a magnetic flux density which causes the creation and movement of ionic charges within the bone tissue. Bone tissue is mainly an ionic-fluid-saturated porous medium having various ions in the intercellular and interstitial fluid such as potassium ions, sodium ions, magnesium ions, chloride ions, phosphate ions, carbonate ions, bicarbonate ions and those formed by the dissociation of amino acids, proteins, sugars, nucleotides and enzymes. The application of a pulsed electromagnetic field, i.e.; the controlled combination of electrostatic and magnetic forces, causes these ions to be charged and moved in a particular direction. The ions diffuse within cells at the treatment area, thereby accelerating the healing process.
According to the present disclosure, the healing of tissue, especially non-union injuries, can be further accelerated by combining ultrasound and E-stim. The forces produced by the applied electromagnetic field add a fluctuating or perturbing force, such as a low frequency modulation force, to the propagating ultrasonic or pressure wave to further stimulate the cells at the treatment area and enhance cellular permeability and ionic diffusion. The largest effect on the acoustic field by the electromagnetic field occurs when the direction of the longitudinal waves is perpendicular to the electromagnetic field, or if the transverse (shear) waves are traveling along the magnetic field lines. The electromagnetic field tends to increase the phase velocity of the ultrasonic waves. The associated magnetic force may be held constant or modulated at a low frequency rate.